U.S. Pat. No. 3,502,149 to Pence discloses that a crosslinked polymeric composition useful as a plugging and sealing agent can be prepared from the mixture of (A) a water soluble or colloid forming polymer from the class consisting of polyacrylamides, polyacrylates, polyacrylic acids, mixtures of acrylates and acids, and sulfonated derivatives thereof; (B) a polyhydric compound whereby a reducing agent in said solution is provided; (C) water; and (D) an oxidizing agent selected from the class consisting of water soluble chromates and dichromates consisting of a solution-soluble hexavalent chromium compound, which yields nascent chromium in situ having a valence state of +3, which crosslink the water-dispersible polymer. The patent discloses that some advantages are obtained when the pH value of the fluid composition is on the acid side such that pH value thereof should be lowered to a value of from 4 to 6 by the addition of acid salts such as aluminum chloride, ferric chloride or calcium chloride, or by the addition of an acid, e.g. hydrochloric or sulfuric acid.
U.S. Pat. No. 3,692,673 to Hoke discloses that polymers of acrylamidosulfonic acids and their salts, especially 2-acrylamido-2-methylpropanesulfonic acid and its salts, are useful as flocculants for aqueous systems, especially in combination with inorganic co-flocculants. The amount of the polymer added to the suspension being flocculated ranges from about 0.01 to about 10 parts per million. The inorganic co-flocculants include ferric sulfate, aluminum sulfate, calcium hydroxide or the like in an amount from about 1 to about 250 parts per million.
U.S. Pat. No. 4,107,057 to Dill, et al. discloses that a well acidizing or fracturing composition is prepared by adding to an aqueous acid solution or emulsion or fracturing composition, a cross-linked copolymer of a sulfonic acid-modified acrylamide or a polyvinyl cross-linking agent. The cross-linked copolymer functions as an effective fluid loss additive and/or diverting agent. From about 25 pounds to about 100 pounds of the additive is utilized per 1000 gallons of the aqueous acid solution or acid emulsion.
U.S. Pat. No. 3,444,037 to Armour discloses an adhesive composition capable of yielding dry films characterized by their optimum water resistance; said composition comprising a mixture of vinyl acetate polymer emulsion, a sulfonated B-stage phenolic resin and an acidic, metal salt curing agent. The preferred curing agents are described as metal salts selected from the group consisting of chromic nitrate, chromic perchlorate, aluminum nitrate and aluminum chloride.